We all noticed how our own tory johnson has slimmed down over the past year. She's written a book about that journey called "the shift," how I lost the weight and discovered a happier life. It's a candid and revealing look how she struggled with her weight. And how she decided to make the shift. Those lines and pounlds have changed her life, pruns and for all. She's our "deals & steals" guru. You love it, right? Reporter: She started two multimillion-dollar businesses. But she's probably best known for empowering women to take charge of their lives. But her own life was out of control. Food has been my entire life, a source of comfort. In good times and bad. Reporter: Always uncomfortable in her own skin, she made excuses. She forged a note from her mom to get out of gym class. Pool parties, no way. Dances, when ever girl wore a dress, I made excuses. Reporter: She wore navy to her own wedding, worrying she would look big in a white dress. She said she almost gave up too quickly. But she was never satisfied with how she looked. Being fat when you don't want to be fat has -- it's like being in shackles. It's like being in a prison and you can't escape. You feel like there's no way out. Reporter: But her aha moment came in the form of a graceful yet candid conversation with someone very important to her. In december 2011, one of my bosses told me that my clothes didn't do me any justice. And she was going to send me to a stylist. She never threatened my career. The word fat, weight, never entered the conversation. But what I took away was, lose weight or lose your job. In that moment, it clicked for me. The lightbulb went off. And I said, I'm going to do it. I'm a smart girl. I'm going to make it happen. Let's go. Well, we see tory every week. And here she looks now. More of her incredible journey. Okay. You have always been beautiful inside and out. You know that from day one. We -- honey, did you see some of those pictures we just showed? It is wonderful to watch. And it's been very natural. We asked you, how much and you never said. You're going to tell us today how much weight you have lost. The last 20 months, 72 pounds. Here's what's the most fascinating to me. That's 20 months. That is almost 3 1/2 pounds a month. If you said to me in the beginning, you're going to go on this thing and lose less than a pound a week. I would have said, just forget it. My whole life, I've been after the quick fix. What I learned in this process, there is no pill, potion or plan that can replace patience and perseverance. That's what the book is all about. I relegal all of the challenges and rye umps to host events. To help other people escape the pain that's shackled me for 40 years. People want to know. There's been tough times during those -- typical afternoon snack, going to starbucks and getting a 400 calorie piece of pound cake. Instead, a pickle. The crazy difference, zero calories. And the most delicious garlic pickles. I've never had one. You had this in lieu of something -- something sweet like that. There you go. In lieu of, I stopped drinking diet soda. I stopped infused water. If you drink one of these waters. It looks pretty, too. It looks gorgeous. A lot of people -- you can drink a lot of calories. Oh, yeah. My biggest weakness is at night, when everyone was asleep. I would sneak into the kitchen and put my hands in a bag of chips or popcorn or whatever was there. And the only thing that saved me was topcoat. I had to polish my nails. I put on the topcoat, with wet nails you can't stick your hands into the bag. And the 20 minutes that it took to dry, the cravings passed and I went to sleep. And a lot is about pausing, before engaging in bad behavior. And the last tip I'll tell you, is no cheat days. Every, single diet says eat what you want during the week and on sunday, go wild. That's akin to an alcoholic celebrating a month of sobriety, with three beers. It doesn't work. My rewards are incredible things. Enjoying flowers and beautiful candles. Katy perry song. Finding other ways to be happy, as opposed to finding the joy in food. Distracting yourself a little bit. Yes. You look amazing. Thank you. Thank you. You guys here, have been so nice to me. We didn't know what was going on. We didn't know you were working on the book. We saw you losing weight. The way you went about it was a way to share. You're a giver. With the "deals & steals." It's wonderful you're doing this for you. "The shift" is on sale today. And you get bonus weight loss tips and to read a chapter, go to goodmorningamerica.Com. You got us teary-eyed. Ginger zee with the weather.

This transcript has been automatically generated and may not be 100% accurate.

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